1. Field of the Invention
This invention relates to a digital signal recording/reproducing apparatus and more particularly to a digital signal recording/reproducing apparatus capable of recording and/or reproducing, along with additional information, a plurality of kinds of digital main information having different data rates from each other.
2. Description of the Related Art
The apparatuses of the kind reproducing records from tape-shaped recording media by means of rotary heads have recently come to include a digital audio tape recorder (abbreviated to DAT), a digital data recorder (DDR), etc., in addition to the video tape recorder (VTR) which is well known. As a result, it has become necessary to arrange the VTR to have some function that is compatible with such various apparatuses.
Such being the background situation, a device for recording, in addition to the conventional analog audio signal, a digital audio signal on an extended part of a video recording track in a time-base compressed state has been developed for the VTR and is now being marketed.
The recording format of the digital audio signal varies with necessary specifications for recording. In other words, since the data rate of the data to be recorded varies according to the necessary specifications, the recording format also varies accordingly. It is, therefore, desirable that the digital audio signal is arranged to be recordable in accordance with any of the audio signal recording formats of varied kinds by the same apparatus (or VTR) while the video signal recording format is arranged to be unvaried.
Generally, in designing a VTR to be capable of recording audio signals in any of various audio signal recording formats, the VTR must be provided with different digital audio signal processing circuits for different data rates respectively. Further, in cases where it is necessary to permit retrieval of the digital audio signal or to have the like function, the VTR must be provided with processing circuits arranged to generate a retrieval signal as additional information and to extract and reproduce the retrieval signal for each of the various recording formats. It is conceivable to process this additional information (or retrieval signal) by the same processing circuit provided for processing the digital audio signal. Generally, however, the additional information to be added for retrieval is preferably recorded and reproduced at a low bit rate for the purpose of facilitating the extracting action thereon.
Therefore, for arranging the VTR to be capable of complying with the audio signal recording formats of varied kinds, the VTR must be provided with processing circuits for processing the audio signals for the various formats and also with processing circuits for processing the retrieval additional information for the various formats. Such arrangement would result in a great increase in the circuit scale of the VTR.